Generators of rotating flow patterns



Nov. 9, 1965 J. v. FOA

GENERATORS OF ROTATING FLOW PATTERNS 3 Sheets-Sheet 1 Filed Jan. 14, 1965 INVENTOR. JOSEPH v. FOA Q/ %u,J

$2 (Ley a-A) ATTORNEYS QQ W Nov. 9, 1965 v. FOA

GENERATORS OF ROTATING FLOW PATTERNS 5 Sheets-Sheet 2 Filed Jan. 14, 1965 INVENTOR. JOSEPH V- FOA ATTORNEYS Nov. 9, 1965 J. v. FOA 3,216,649

GENERATORS 0F ROTATING FLOW PATTERNS Filed Jan. 14, 1965 3 Sheets-Sheet 3 INVENTOR. JOSEPH V. FOA

BYQV 4754 TW ATTORNEYS United States Patent 3 216 649 GENERATORS 0F RdTATlNG FLOW PATTERNS Joseph V. Foa, Troy, N.Y., assignor to the United States gt America as represented by the Secretary of the Air orce Filed Jan. 14, 1965, Ser. No. 425,644 7 Claims. (Cl. 230-1) This is a continuation-in-part of application Serial No. 213,560, filed July 30, 1962, now abandoned.

The present invention relates to a method of direct energy transfer of mechanical energy from one steady fluid flow to another by means of moving pressure fields, and more particularly, to the process and apparatus for generation of rotating pseudo-blade patterns wherein mechanical moving parts may 'be dispensed with.

If a fluid under pressure is discharged through an opening in a rotating body, a pressure field is generated by the interaction between the issuing (primary) stream and the surrounding (secondary) fluid. If the interaction space communicates with a source of secondary fluid and is so confined that significant portions of the interacting streams are forced to deflect each other to a common orientation in a coordinate system fixed to the rotating body, energy is transferred from the primary to the secondary stream in a stationary frame of reference. This method of direct transfer of energy from one fluid flow to another is described in US. Patent No. 3,046,732.

At every instant of this process, the driving fluid which has emerged in an immediately preceding time interval from the rotating orifice, is found to occupy a spiral or helical region in space, which rotates about the same axis and at the same angular velocity as the rotor. Although the fluid particles within this region do not follow this same motion, its boundaries are the interfaces separating the driving from the driven fluid and their rela tion to the induced flow pattern is therefore substantially the same as that of blade or vane surfaces of the same shape, rotating at the same angular velocity. Thus the driving fluid forms a pseudo-blade, the action of which on the driven fluid is somewhat similar to the flow induction process of solid blades or vanes in dynamic flow machines. In the same manner, if the driving fluid is discharged through a plurality of orifices, the discharged particles may be viewed as forming a pseudo cascade.

In elfect, the energy extracting action of a turbine and the energy adding action of a propeller or pump or compressor are here compounded in a single step, whereby energy is transferred from one fluid to the other di rectly, without the intermediary conversion to shaft work and the attendant mechanical devices. If the orientation of the primary discharge nozzle is skewed to the axis of rotation, the energy acquired by the secondary fluid in this process of flow induction is extracted entirely or partially from the primary flow, depending on whether the rotation of the body is produced and main tained solely by the reaction of the issuing jet or whether some augmenting means if employed. The application of a torque to the rotor would result in a modification of the energy level of the driving flow, but in any case the transfer of energy from the driving to the induced flow is a process which takes place outside of the rotor, as a direct exchange through the boundaries of the pseudoblades.

For example, the function of a propeller or fan may be provided by discharging the primary fluid and capturing the secondary fluid into an annular interaction duct extending axially between the rotor and a concentrically arranged outer bounding surface or shroud. Similarly, the function of a radial-flow pump may be provided by confining the interaction space within an assembly much like the casing of a conventional centrifugal compressor.

The object of the present invention is the provision of a method and apparatus for producing the above described rotating pseudo-blade pattern without the use of a rotor or other moving mechanical parts. This objective is achieved by making unique use of the phenomenon of stalling, a phenomenon heretofore found to be an adverse element. In the inventive concept, the fluid flow passage is past a cascade of vanes located, for example, radially between two stationary bodies. The vanes are arranged in a cascade at the stalling angle of attack relative to the radial direction of flow.

The phenomenon of stalling, and pertinent to the present invention, the phenomenon of rotating stall has been the subject of investigations wherein it was shown that when the angle of attack of compressor rotor vanes becomes too large as a result of an excessive reduction of the oncoming flow velocity, the flow in the rotor passages stalls in one or more regions encompassing several blade passages. These stalled regions rotate, relative to the rotor, at an angular velocity which is lower than that of the rotor and of the opposite sign. Therefore, in a frame of reference which is fixed to the stationary parts of the machine, they appear to be rotating at a speed which is lower than the rotor speed but in the direction of rotor rotation.

The mechanism of rotating stall may be qualitatively explained by considering a cascade of rotor blades, represented as straight vanes exposed to a flow, the relative velocity vector of which forms, with the orientation of the vanes, an angle which is close to the stalling angle of attack of the vanes. When a perturbation of the incoming flow causes the angle of attack to increase on one vane, stall may be initiated there. The flow then separates from the dorsal side of the effected vane, thereby reducing the elfective cross-sectional area of the passage on that side. The resulting blockage of the flow causes the diversion of some of the entering fluid to neighboring passages, thereby increasing the angle of attack on one side and decreasing it on the other side of the affected passage. Thus the stall propagates along the cascade, as new passages become stalled on the side where the angle of attack is increased and unstalled on the other side. A steady state is soon established, whereby the stalled region, comprising a fixed number of passages, travels through the cascade at a constant rate. In an annular cascade, one or more, evenly spaced, stall zones are formed in this manner; and these zones propagate around the axis of the cascade, and there is produced a rotating stall.

Heretofore this type of stall has been considered very undesirable in compressors because it causes a decrease in pressure rise and causes flow fluctuations which may lead to resonant excitation and blade failure. What the invention has accomplished is the utilization of this phenomenon to generate rotating pseudo-blades useful in fluid induction systems, and without the use of a rotor or any other mechanically moving elements heretofore found necessary.

The applications of the invention are numerous. It may be applied to gases and liquids, to fluids containing solid particles or objects in suspension and even to any aggregate of solid particles (such as sand or gravel) which can be made to flow. The energy exchange which is accomplished by this process can be useful in the generation of thrust, in pumping, compressing, supercharging, transporting, dredging and drilling systems, in the extraction of energy from flowing fluids, in the handling of high temperature, erosive or corrosive fluids, in

flow induction systems where the use of ejectors is undesirable either because of their low efficiency or because the interacting fluids require separate handling after the energy exchange; and, more generally, in the transfer of energy from one flow to another for any purpose whatsoever.

These and other advantages, features and objects of the invention will become more apparent from the following description taken in connection with the illustrative embodiments in the accompanying drawings wherein:

FIGURE 1 is a graphic representation of the phenomenon of stall;

FIGURE 2 is a graphic representation of the phenomenon of rotating stall utilized in the present invention;

FIGURE 3 is a longitudinal section of a device for the production of rotating pseudo-blades for exchange of energy from a primary fluid to a secondary fluid and for containment of the interaction space;

FIGURE 4 is a schematic cross-section taken substantially on the line 4-4 of FIGURE 3 and showing portions broken away;

FIGURE 5 is a longitudinal section of a modification of the device;

FIGURE 6 is a schematic cross-section taken substantially on the line 66 of FIGURE 5 with portions broken away;

FIGURE 7 is a fragmentary elevational view, partly in cross-section, of a further modification of the device for producing and utilizing rotating pseudo-blades showing an axial flow arrangement; and

FIGURE 8 is a still further modification of a device for producing and utilizing rotating pseudo-blades in an axial flow arrangement, and showing specifically an interaction space and a containment for the secondary fluid.

Referring more in detail to FIGURES 1 and 2 of the drawing, a cascade of straight rotor blades or vanes 10 with a peripheral velocity V are exposed to an incoming flow whose absolute velocity is A. The flow velocity relative to the vanes, represented vectorially as B in FIGURE 1, is inclined to the vanes at an angle 0 which is near their stalling angle of attack.

As described above, if a perturbation causes the flow to separate from the dorsal side of some vanes as indicated in dotted lines 12 in FIGURES 1 and 2, the fluid which is blocked from entering the affected passages is diverted upstream to the adjacent passages, causing an increase of the angle of attack on one side (arrow C in FIGURE 2) and to decrease on the opposite side (arrow D, FIGURE 2). The stalled region indicated at E in FIGURE 2, propogates from right to left as seen in FIG- URE 2, an additional passage stalling, as the last stalled passage to the rear of the moving stalled region becomes unstalled.

Referring to FIGURES 3 and 4, a pseudo-blade generator is indicated generally by the numeral 14. A stationary inlet conduit casing 16 and a shallow cone shaped end member 18 serving as a baflie, are connected by a cascade of vanes 20'. The complementary formation of the stationary members 16 and 18 creates an annular passageway 22 flared radially outwardly from a central duct 24 and divided into peripheral passageways by the vanes 20.

The vanes 20 are arranged at the stalling angle of attack relative to the radical direction of flow, and are so closely spaced that the flow is substantially stopped in the stalled passages. The fluid issuing through the unstalled passages will form rotating pseudo-blades, shown at 26, in the annular surrounding space. The present invention employs the blades 26 to transmit energy to fluid material located in this interaction space indicated generally by the numeral 27 FIGURES 3 and 4. A lipmember 28 defines a threat 29 for conducting the secondary fluid into the interaction space 27.

The modification shown in FIGURES 5 and 6 is similar in all respects to the device disclosed in FIGURES 3 and 4 except that an additional set of adjustable vanes 30 is added to provide direction to the flow before it strikes the vanes 20'. The inlet conduit casing member 16 and conical end member 18 are positioned radially as in FIGURES 3 and 4. The required angle of attack, however, is obtained by means of the adjustable vanes 30 which are positioned radially inwardly from the vanes 20'. The flow from the conduit 24' is redirected to encounter the vanes 20' at an angle in excess of the stalling angle. The moving stalled regions are produced in the manner described above, and the rotating pseudo-blade effect is obtained. In the present invention the pseudoblades are utilized for the modification of a secondary fluid which is introduced into an interaction space indicated at 29 in FIGURES 5 and 6, and bounded by the radially outward portion of the member 18 and throat member 29.

In the modification of the device shown in FIGURE 7, the rotating pseudo-blade effect is obtained in an axial flow arrangement. An inner body 31 is arranged coaxially with a cylindrical outer body 32 to form a flow area therebetween. Members 31 and 32 are connected by a cascade of vanes 34.

The relationship of velocity of flow to vane angle is governed to provide the moving stall area and the consequent revolving pseudo-blades.

In the modification shown in FIGURE 8, the flow is an axially directed flow, and is similar to that shown in FIGURE 7 with an added element for controlling the angle of attack of the flow on the vanes 34. An inner body 31' and an outer co-axial cylinder 32' provide the flow conduit 36'. The connecting vanes 34 on the periphery of the body 31' are parallel to the axis of the body 31', and therefore parallel to the direction of flow in the flow area 36. Redirection is accomplished by the vanes 38 so that the flow enters each passage formed by the vanes 34 at an angle near the stalling angle, and the condition of a moving stall area and rotating pseudoblades is established. The pseudo-blades in each modification of FIGURES 7 and 8 operate to transfer energy to a secondary fluid confined in the space 40 of FIGURE 7 and 40' of FIGURE 8 defined by the containment elements 42 and 42', respectively, which are indicated only schematically, and may be of any expedient form, applicable to a specific use.

The devices thus far described may be further modified by rotatably mounting the bodies so that, together with their peripherally mounted vanes, they form rotors. These rotors may be driven about their axes by the reaction of the issuing jets, or by other means. The angular velocity of the pseudo-blades formed by the generator will then be equal to the sum of the angular velocity of the cascade and the angular velocity of stall propagation relative to the cascade. In this case, the setting of the vanes must be such that their inclination to the relative incoming flow becomes equal to the stalling angle of attack when they are rotating.

The issuing pseudo-blades which rotate around the bodies may be utilized to propel the bodies in a fluid medium or, alternatively, when the entire unit is housed within an additional container the pseudo-blades would form a spiral along the container thereby creating a pumping action.

Although the invention has been described with reference to a particular embodiment, it will be understood to those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claims.

What I claim is:

1. In an energy exchanger for direct transfer of energy from a primary fluid to a secondary fluid, a pair of stationary bodies spaced to form a passage for a flow of said primary fluid therebetween, primary fluid material flowing in said passage at a predetermined rate, a cascade of vanes positioned between said bodies, means defining an interaction space communicating with a source of said secondary fluid and adapted to be occupied thereby, said vanes forming passages for discharging said primary fluid into said interaction space, the orientation of said vanes relative to the approaching flow of said primary fluid being such that the cascade operates in a condition of rotating stall, said vanes being so closely spaced that said flow of primary fluid is substantially stopped in the stalled passages, the propagating unstalled passages forming areas through which said primary fluid issues into said interaction space in much the same manner as if it were issuing through laterally moving orifices, thereby forming pseudo-blades for transferring energy to said secondary fluid in said interaction space.

2. In a generator of pseudo-blades of a primary fluid for interaction with a secondary fluid in an interaction space according to claim 1, a stationary conduit body member having an outwardly flared open end, an end member, said cascade of vanes connecting said conduit member and said end member and positioned adjacent the periphery of said conduit member and said end member, said conduit member and said end member forming a radial passage divided by said vanes into a series of passages leading to an interaction space, means defining said interaction space, a flow of said primary fluid material entering said conduit at a predetermined rate and being deflected radially by said end member, the orientation of said vanes relative to said deflected flow being such that the cascade operates in a condition of rotating stall, rotating pseudo-blades of primary fluid, said blades being formed in said interaction space by said condition of rotating stall and functioning to transfer energy to the secondary fluid present in said interaction space.

3. In a generator of pseudo-blades of primary fluid for interaction with a secondary fluid according to claim 1, a conduit body member having an outwardly flared open end, an end member positioned with reference to said conduit body member to form a radial annular passageway, said cascade of radial vanes being positioned adjacent the periphery of said passage, and dividing said passageway into a plurality of outlet passageways, a second cascade of vanes positioned in said annular passageway and spaced radially inwardly from said first mentioned cascade, fluid flowing in said conduit and through said annular passageway at a predetermined rate, the vanes of said second cascade being so adjusted that they deflect said flow to such an orientation relative to the first cascade that said first cascade operates in a condition of rotating stall, thereby forming pseudo-blades for the transfer of energy to the secondary fluid present in said interaction space.

4'. In a generator of pseudo-blades according to claim 1, an inner cylindrical body and an outer cylindrical body of differing diameters arranged concentrically to provide flow space therebetween, a fixed rate of flow of primary fluid in said flow space, said cascade of vanes connecting said body at or near the extremity of said outer body, the orientation of said vanes relative to said flow being such that said cascade operates in a condition of rotating stall, thereby forming pseudo-blades for interaction and transfer of energy from said primary fluid to the secondary fluid contained in said interaction space.

5. In an energy exchanger for direct transfer of energy from a primary fluid to a secondary fluid, a pair of stationary bodies spaced to form a passage for a flow of said primary fluid therebetween, primary fluid material flowing in said passage at a predetermined rate, a cascade of vanes positioned between said bodies, means defining an interaction space communicating with a source of said secondary fluid, and adapted to be occupied thereby, said vanes forming passages for discharging said primary fluid into said interaction space, the orientation of said vanes relative to the approaching flow of said primary fluid being such that the cascade operates in a condition of rotating stall, said vanes being so closely spaced that said flow of primary fluid is substantially stopped in the stalled passages, the propagating unstalled passages forming areas through which said primary fluid issues into said interaction space in the same manner as if it were issuing through laterally moving orifices, whereas the regions downstream of said stalled passages receive said secondary fluid from said source, whereby laterally moving streams of said primary fluid are formed in the interaction space and laterally moving stream of said secondary fluid are formed therebetween, energy and momentum being transferred from said primary fluid to said secondary fluid through forces acting normal to the interfaces therebetween.

6. In an energy exchanger for direct transfer of energy from a primary fluid to a secondary fluid, a pair of coaxial cylindrical stationary bodies of diflering diameters spaced to form a passage for a flow of said primary fluid therebetween, primary fluid material flowing in said passage at a predetermined rate, a cascade of vanes positioned between said bodies, said vanes forming passages for discharging said primary fluid into an interaction space connected to a source of secondary fluid, confining means for confining said secondary fluid in said interaction space, the orientation of said vanes relative to the approaching flow of said primary fluid being such that the cascade operates in a condition of rotating stall, said vanes being so closely spaced that said flow of primary fluid is substantially stopped in the stalled passages, the propagating unstalled passages forming areas through which said primary fluid issues into said interaction space in much the same manner as if it were issuing through laterally moving orifices, thereby forming pseudo-blades in said interaction space.

7. In an energy exchanger for direct transfer of energy from a primary fluid to a secondary fluid, a pair of coaxial cylindrical stationary bodies of diflering diameters spaced to form a passage for a flow of said primary fluid therebetween, primary fluid material flowing in said passage at a predetermined rate, a cascade of vanes positioned between said bodies, said vanes forming passages for discharging said primary fluid into an interaction space connected to a source of secondary fluid, confining means for confining said secondary fluid in said interaction space, the orientation of said vanes relative to the approaching flow of said primary fluid being such that the cascade operates in a condition of rotating stall, said vanes being so closely spaced that said flow of primary fluid is substantially stopped in the stalled passages, the propagating unstalled passages forming areas through which said primary fluid issues into said interaction space in much the same manner as if it were issuing through laterally moving orifices, thereby forming pseudo-blades in said interaction space, a second cascade of vanes spaced upstream from said first mentioned cascade, fluid flowing in said conduit at a predetermined rate, the vanes of said second cascade being so adjusted that they deflect said flow of primary fluid to such an orientation relative to the first cascade that said first cascade operates in a. condition of rotating stall, the rotating pseudo-blades of primary fluid thus formed functioning to transfer energy to said secondary fluid in said interaction space.

OTHER REFERENCES Transactions of the A.S.M.E., May 1958, pages 777 to 790 inclusive, volume (1958).

LAURENCE V. EFNER, Primary Examiner. 

1. IN AN ENERGY EXCHANGER FOR DIRECT TRANSFER OF ENERGY FROM A PRIMARY FLUID TO A SECONDARY FLUID, A PAIR OF STATIONARY BODIES SPACED TO FORM A PASSAGE FOR A FLOW OF SAID PRIMARY FLUID THEREBETWEEN, PRIMARY FLUID MATERIAL FLOWING IN SAID PASSAGE AT A PREDETERMINED RATE, A CASCADE OF VANES POSITIONED BETWEEN SAID BODIES, MEANS DEFINING AN INTERACTION SPACED COMMUNICATING WITH A SOURCE OF SAID SECONDARY FLUID AND ADAPTED TO BE OCCUPIED THEREBY, SAID VANES FORMING PASSAGES FOR DISCHARGING SAID PRIMARY FLUID INTO SAID INTERACTION SPACE, THE ORIENTATION OF SAID VANES RELATIVE TO THE APPROACHING FLOW OF SAID PRIMARY FLUID BEING SUCH THAT THE CASCADE OPERATES IN A CONDITION OF ROTATING STALL, SAID VANES BEING SO CLOSELY SPACED THAT SAID FLOW OF PRIMARY FLUID IS SUBSTANTIALLY STOPPED IN THE STALLED PASSAGES, THE PROPAGATING UNSTALLED PASSAGES FORMING AREAS THROUGH WHICH SAID PRIMARY FLUID ISSUES INTO SAID INTERACTION SPACE IN MUCH THE SAME MANNER AS IF IT WERE ISSUING THROUGH LATERALLY MOVING ORIFICES, THEREBY FORMING PSEUDO-BLADES FOR TRANSFERRING ENERGY TO SAID SECONDARY FLUID IN SAID INTERACTION SPACE. 